1. Field of the Invention
The present invention relates to a circuit module including a plate-shaped circuit carrier of glass or ceramic and having a metal plate which is connected over a large area to one side of the circuit carrier. The metal plate is constructed as a three-layer plate having two outer layers of essentially the same thickness which consist, in each case, of a metal with good thermal conductivity, or a metal alloy with good thermal conductivity. The center layer of the metal plate constructed from a material having a much poorer thermal conductivity compared with the conductivity of the two outer layers. The coefficients of thermal expansion of the layers are matched in such a manner that the resultant coefficient of the three-layer plate largely corresponds to the coefficient of thermal expansion of the circuit carrier.
2. Description of the Prior Art
The aforementioned construction of a circuit module provides the advantageous possibility of constructing the metal plate to be relatively thick thereby making it suitable for removing relatively large quantities of heat without, as a result, shear forces occurring between the circuit carrier and the metal plate. As has heretofore been the case, such shear forces cause the adhesive or solder bond between the metal plate and the circuit carrier to tear. Moreover, when the area of the metal plates is increased in order to remove large amounts of heat, the outer metallic conductive layer is not adequately involved in the heat transport.